1 /**
2 * This file Copyright (c) 2011 Magnolia International
3 * Ltd. (http://www.magnolia-cms.com). All rights reserved.
4 *
5 *
6 * This file is dual-licensed under both the Magnolia
7 * Network Agreement and the GNU General Public License.
8 * You may elect to use one or the other of these licenses.
9 *
10 * This file is distributed in the hope that it will be
11 * useful, but AS-IS and WITHOUT ANY WARRANTY; without even the
12 * implied warranty of MERCHANTABILITY or FITNESS FOR A
13 * PARTICULAR PURPOSE, TITLE, or NONINFRINGEMENT.
14 * Redistribution, except as permitted by whichever of the GPL
15 * or MNA you select, is prohibited.
16 *
17 * 1. For the GPL license (GPL), you can redistribute and/or
18 * modify this file under the terms of the GNU General
19 * Public License, Version 3, as published by the Free Software
20 * Foundation. You should have received a copy of the GNU
21 * General Public License, Version 3 along with this program;
22 * if not, write to the Free Software Foundation, Inc., 51
23 * Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
24 *
25 * 2. For the Magnolia Network Agreement (MNA), this file
26 * and the accompanying materials are made available under the
27 * terms of the MNA which accompanies this distribution, and
28 * is available at http://www.magnolia-cms.com/mna.html
29 *
30 * Any modifications to this file must keep this entire header
31 * intact.
32 *
33 */
34 package info.magnolia.registry;
35
36 import org.apache.commons.lang.StringUtils;
37
38 import java.util.ArrayList;
39 import java.util.Collection;
40 import java.util.HashMap;
41 import java.util.HashSet;
42 import java.util.Map;
43 import java.util.Set;
44
45 /**
46 * Thread safe map intended to be used for registries. Provides an atomic operation <code>removeAndPutAll</code> that is
47 * used to remove a set of previously added values before adding a collection of new ones. Read operations are blocked
48 * until it completes guaranteeing proper visibility.
49 * <p/>
50 * It is common for entities in registries to also hold their identifier. The method <code>keyFormValue</code> can be
51 * overridden to get the identifier from the value. This removes the need to package a set of entities that should be
52 * added in a Map before calling {@link #removeAndPutAll(java.util.Collection, java.util.Map)}.
53 *
54 * @param <K> the type of keys maintained by this map
55 * @param <V> the type of mapped values
56 * @version $Id$
57 */
58 public class RegistryMap<K, V> {
59
60 private final Map<K, V> map = new HashMap<K, V>();
61
62 public synchronized V get(K key) {
63 return map.get(key);
64 }
65
66 public synchronized V getRequired(K key) throws RegistrationException {
67 V value = map.get(key);
68 if (value == null) {
69 throw new RegistrationException("Entry for [" + key + "] not found in registry, available entries are: " +
70 (map.isEmpty() ? "<none>" : StringUtils.join(map.keySet(), ", ")));
71 }
72 return value;
73 }
74
75 public synchronized void put(K key, V value) {
76 map.put(key, value);
77 }
78
79 public synchronized void put(V value) {
80 map.put(keyFromValue(value), value);
81 }
82
83 public synchronized void remove(K key) {
84 map.remove(key);
85 }
86
87 public synchronized void removeAndPutAll(Collection<K> toRemove, Map<K, V> toPut) {
88 // Fail early if the keyFromValue method hasn't been overridden
89 if (!toPut.isEmpty()) {
90 keyFromValue(toPut.values().iterator().next());
91 }
92 for (K key : toRemove) {
93 map.remove(key);
94 }
95 map.putAll(toPut);
96 }
97
98 public synchronized Set<K> removeAndPutAll(Collection<K> toRemove, Collection<V> toPut) {
99 if (!toPut.isEmpty()) {
100 keyFromValue(toPut.iterator().next());
101 }
102 for (K key : toRemove) {
103 map.remove(key);
104 }
105 HashSet<K> keys = new HashSet<K>();
106 for (V value : toPut) {
107 K key = keyFromValue(value);
108 map.put(key, value);
109 keys.add(key);
110 }
111 return keys;
112 }
113
114 public synchronized Collection<K> keySet() {
115 return new ArrayList<K>(map.keySet());
116 }
117
118 public synchronized Collection<V> values() {
119 return new ArrayList<V>(map.values());
120 }
121
122 protected K keyFromValue(V value) {
123 throw new UnsupportedOperationException("keyFromValue");
124 }
125 }